Sink Holes - What Am I Doing Wrong?

[flyingcross]

In the last three weeks I have gone through more plaster of paris than I did in cub scouts 45 years ago. I have made several molds and have successfully poured some stick baits. When I pour the larger stick baits, (Yum Dinger 7.25 inch), the bait comes out fine with the exception that I get a sink hole (hollow middle) in the last 1-1.5 inches of the bait toward the pour hole.

I must say that not always. Sometimes I get the full bodied bait that I am looking for, but probably 75% of the time I am not satisfied. I am remelting same color plastic worms in the microwave and pouring out of a pyrex cup. This sink hole doesn't seem to happen when I pour the 5 inch Senko style baits.

Am I not heating the plastic long enough and it is cooling down by the time I reach the top of the larger mold? Is using the remelted worms instead of plastisol causing this? Or could this be an air venting problem in the mold itself?

If I have learned anything about this hobby, it is that is is definately a trial and error process. And the wealth of information on this forum is endless. If any of you can guide a newbie in this area, I would certainly appreciate your input.

Pat

[BBK]

How big is your sprew (sp?) and do you top them off?

[flyingcross]

How big is your sprew (sp?) and do you top them off?

The pour hole is about the diameter of the Yum Dinger and yes I do pour until the plastic fills up the top. The mold has two Senko style and 2 yum Dinger cavities.

[BBK]

The pour hole is about the diameter of the Yum Dinger and yes I do pour until the plastic fills up the top. The mold has two Senko style and 2 yum Dinger cavities.

Ok, you need to keep topping off the mold as the bait sucks the plastic down. That is what is causing your hollow spots.

[flyingcross]

Ok, you need to keep topping off the mold as the bait sucks the plastic down. That is what is causing your hollow spots.

Thanks BBK, I will try that.

[gunnie3035]

Thanks BBK, I will try that.

You can also use this to your advantage by pouring a different color of plastic before it sucks down to far. It can give you a totally different look on a translucent base color.

[bluegrasslover]

You can also use this to your advantage by pouring a different color of plastic before it sucks down to far. It can give you a totally different look on a translucent base color.

That's a great idea! I know I've had some that have sink holes 2-3" down. Topping it off with another color could look pretty cool!

[mark poulson]

That sounds like it would make "core shot" baits like the green pumpkin/chartruese senko.

[criggster]

I had the same problem when I started pouring. Two things solved it: bigger sprue hole and topping off the sprue as the bait cools and pulls the plastic down into the mold.

[flyingcross]

I had the same problem when I started pouring. Two things solved it: bigger sprue hole and topping off the sprue as the bait cools and pulls the plastic down into the mold.

Thanks.....Appreciate the feedback

[gunnie3035]

That sounds like it would make "core shot" baits like the green pumpkin/chartruese senko.

Instead of filling the mold all the way to the top of the sprue stop as soon as you get to the opening of the spuce. The plastic will suck down faster and deeper into the bait. Then pour in the 2nd color quickly and fill to the top of the sprue. I use this all the time on swimbaits to give the head a different color. It can be used on any mold poured from the nose.